1. Field of the Invention
This invention relates to a method for depositing a film by using a deposition gas, a method of selective etching by using an etching gas, charged particle beam equipment for these methods, a method for manufacturing a large scale integration (LSI), and a technology of LSI manufacturing equipment. More particularly, the present invention relates to technology that is effective when being applied to a method for depositing a film by using a deposition gas and a focused ion beam (FIB) or a method for performing selective etching by using an etching gas and a FIB.
2. Discussion of Background
A conventional FIB apparatus can scan the surface of a sample with the FIB, detect secondary electrons and secondary ions generated from the sample surface, and observe a minute region of the sample surface from their profiles. Moreover, the FIB apparatus can perform sputter etching on the sample surface by scanning the sample surface with the FIB. Furthermore, by introducing a gas used for making a thin film into a sample chamber, spraying it on the sample surface, and simultaneously scanning the sample surface with the FIB, the apparatus can decompose this raw material gas and form a metal film, among other things, by deposition on the sample surface in an FIB scanning region. This film deposition method is called the FIB assisted deposition (FIBAD) method. In addition, when performing sputter etching, if an etching gas is sprayed on the substrate, the etching rate for each substrate constituent material can be increased or decreased as desired. This etching method is called the selective etching method. The FIBAD method and the selective etching method are widely used.
FIG. 1 is a view showing FIB scanning and a method for introducing a gas used in the FIBAD method and in the selective etching method. A gas is introduced to a substrate 21 locally from a nozzle 12. By bringing the nozzle 12 close to an FIB irradiation position, the quantity of gas adsorbed by the substrate 8 can be increased. In the FIBAD method and in the selective etching method, a gas used as a raw material (deposition gas or etching gas) is sprayed from the nozzle 12, and the FIB is scanned in a desired scanning region 18.
FIG. 2 shows a method for scanning FIB 11. The FIB 11 has a limited probe size 14 on the surface of the substrate 8. The deposition gas 15 introduced from the nozzle 12 is adsorbed on the surface of the substrate 8. The FIB 11 stays at a scan lattice point 16 for a constant time, and then moves to the adjacent scan lattice point 16 away from the scan lattice point 16 by the distance of a scan spacing 17. Generally, the scan spacing 17 is set in conformity to the probe size 14 of the FIB, that is, to 10 nm to 1000 nm. Repeated scanning of the scanning region 18 by the above-mentioned technique makes the irradiation density of the FIB uniform, and simultaneously realizes uniformity of the film thickness that is formed by deposition in the FIBAD method or uniformity of etching depth in the selective etching method.
As a technology of equalizing the thickness of a film formed by the FIBAD method, there are the following prior arts. A first example (JP-A No. 298243/1996) discloses a FIBAD method for effectively equalizing the whole quantity of FIB irradiation on the sample surface in the case where there is inclination or holes on the whole surface of a sample on which a film is intended to be accumulated by changing the quantity of FIB irradiation according to an effective area irradiated with the FIB. A second example (JP-A No. 289133/1991) discloses a technology of equalizing the thickness of a film that is accumulated by controlling scanning conditions of a beam (beam scanning speed, scanning pitch, and scanning pattern) according to beam conditions of the FIB (acceleration voltage and beam current).
Further, as a technology of equalizing the etching rate in the case where selective etching is performed using the FIB, there are the following prior arts. A third example (JP-A No. 120153/1997) discloses a technology of moving the FIB irradiation spot to the outside of the scanning region and halting the FIB irradiation for a predetermined time until sufficient etching gas is supplied to the adjacent irradiation spot when the FIB irradiation spot is moved to the adjacent irradiation spot. During this period, the FIB is blanked, and hence is not allowed to irradiate a moved position of the beam spot. Because of this, the etching rates in the irradiation spot and in a superposed position are equalized. A fourth example (JP-A No. 29201/2000) discloses a technology in which the etching rate have been obtained in advance for different kinds of processing parts (area, position, and shape) and the number of shots of FIB irradiation is decided according to a processing part.